The proposed experiments will investigate the effects of visual cortex damage on the neurophysiology of related brain regions. Electrophysiological recordings will be made of the responses of single neurons in these regions to specific visual stimulation. The first objective of these experiments is to study the nature of the visual cortex inputs to these brain regions. The second objective is to investigate the possibility that there is a reorganization of the physiological responses of these cells following long recovery periods from the visual cortex damage. These studies will increase our understanding of the mechanisms of recovery of function after brain damage. Two projects are proposed, as follows: Previous experiments which I have conducted demonstrated a behavioral reorganization of the function of the middle suprasylvian cortex of the cat following long- term damage to the visual cortex. The first project to be proposed will investigate the short-term and long-term effects of visual cortex damage in the cat on the receptive field characteristics of cells in the middle suprasylvian cortex. Anatomical studies indicate that there is a structural reorganization of the optic tract inputs to the ventral geniculate nucleus of the rat following long-term visual cortex damage. Similar sprouting phenomena in one brain region as a consequence of damage to another brain region have been reported by a number of investigators. However, the physiological significance of these anatomical alterations is unknown. The second project will investigate the receptive field characteristics of single neurons in the ventral lateral geniculate nucleus of the rat, followed by an investigation of the effects of short- term and long-term visual cortex removal.